Motor skill learning and other goal-directed behavior involves defining a goal and practice. During practice, neural circuits evaluate sensory feedback and guide adaptive changes in motor control circuitry. An important example of such behavior is displayed by the small number of species, including humans that learn vocalizations crucial to communication. Neural mechanism of vocal learning are best understood in songbirds, where vocal learning requires a discrete region of the basal ganglia, Area X. The neurotransmitter dopamine plays a crucial role in basal ganglia function and plasticity, but dopamine release has not been measured in behaving songbirds and the function of dopamine in vocal learning in unknown. The goals of this project are to determine the temporal features of dopamine signals required for synaptic plasticity in Area X and then to ask in behaving songbirds if such dopamine signals occur during memorization of a song to mimic or during auditory-feedback dependent plasticity of vocal control circuits. Since song learning involves a well-defined neural circuit devoted to a single behavior, these studies may offer unique insights into the mechanisms by which dopamine and the basal ganglia contribute to motor learning in all vertebrates. The importance to human health of understanding the function of basal ganglia dopamine is underscored by the devastating effects of dopamine loss in Parkinson's Disease and pharmacological mis-activation by drugs of abuse. [unreadable] [unreadable] [unreadable]